The natural distribution of thermotolerant Campylobacter sp. in dogs (150 stray animals and 64 pets) was studied. Campylobacters were more frequently isolated (p<0.01) from stray dogs (51.3%) rather than from pet dogs (21.9%). All the biotypes described by Lior for C. jejuni and C. coli were found among stray animals, whereas only C. jejuni biotypes I and II and C. coli biotype II were found among pet dogs. The need for more studies related to the role of environmental sanitary conditions in the spreading of Campylobacter species is noted.

Campylobacter jejuni and C. coli are prevalent agents of gastroenteritis in human beings, especially in developing countries2,5. They have been isolated from water, sewage, food of animal origin and from a great variety of domestic and wild animals and birds2,6,15. These can come into frequent contact with humans, as in the case of pets and animals or birds used as food.

Transmission of Campylobacter sp. to human beings involves the consumption of contaminated food or water, the handling of raw chickens and direct contact with infected animals or their feces2,15. Cats and dogs have been described as sources of infection, particularly for children1,12,14,16.

Having in mind that remarkable differences have previously been observed in the intestinal carriage of Campylobacter among stray and pet dogs3,13, and the lack of information about this epidemiological aspect in developing countries, the natural distribution of thermotolerant Campylobacter sp. in these two types of dogs in southern Chile was studied.

Material and Method

The study was conducted in Valdivia city (140.000 inhabitants, 73°11'W, 39°46'S) during a 6 - month period (April to August, 1990).

Two hundred and fourteen animals were studied: 150 stray dogs and 64 pet dogs. Pet dogs are those animals having known owners and mantained in permanent confinement. Animals without a known owner, or even having one, but presenting wandering habits, were considered as stray dogs.

All the dogs were examined in the Universitary Veterinary Clinic where fecal samples were taken from each animal by means of a rectal swab. None of them presented diarrheal symptomatology.

Each sample was identified with an appropiate code number and within 2 to 3 hours after collection was seeded on modified Skirrow's medium comprising Brucella agar, 5% horse blood, Skirrow's antibiotic supplement (Oxoid) plus 10 µg/ml of cephalotin an 2 µg/ml of amphotericine B and FBP supplement (Oxoid). Inocculated plates were incubated at 43°C for 48 hours under microaerobic conditions utilizing the Anaerocult C system (Merk).

After the incubation period, plates were examined and Campylobater species and biotypes were identified using the criteria proposed by Lior10.

Results

Campylobacter species were isolated from 91 (42.5%) animals. Seventy seven (51.3%) of these were stray dogs and 14 (21.9%) had known owner (pet dogs).

All the biotypes described by Lior10 for C. jejuni and C. coli were found in stray dogs, C. jejuni biotypes I and II and C. coli biotype I being the most frequent (38.9%, 29.6% and 60.9%, respectively).

Among the dogs with known owners the distribution of the biotypes of C. jejuni and C. coli was more restricted. Only C. jejuni biotypes I and II (55.6% and 44.4% respectively) and C. coli biotype II (100%) were isolated from these animals.

Table shows the distribution of Campylobacter isolates among both groups of dogs.

Discussion

Infected animals may be involved in the spread of Campylobacter species to man2. Dogs and others companion animals have been shown to be sources of infection2,4,12,14,16.

In the present study, the frequency of stray dogs harboring Campylobacter species was of 51.3%. This value is similar to that obtained by Simpson et al13. and Bruce and Zochowski3 for the same type of animals. On the other hand, as Simpson et al13. have found, this study showed that the number of animals with Campylobacter in their feces was significantly greater in stray than in pet dogs. However, a higher number of carriers was found among pets than in the study of Simpson et al13.

Fox et al9. stated that the isolation rates of Campylobacter in certain dog populations may reflect the inadequate environmental sanitation prevailing where the animals are living or maintained. So when sanitation and housing are often less than ideal, the animals have considerable opportunities for cross-contamination.

When Lior's10 biotyping scheme was applied to Campylobacter strains isolated from stray dogs, the 4 biotypes described for C. jejuni and the 2 for C. coli were found. Among the strains isolated from pet dogs, the biopyte distribution for both Campylobacter species was more restricted. Only C. jejuni biotypes I and II and C. coli biotype II were found.

The latter biotypes are the most frequently isolated from cases of human diarrhea in Valdivia city2 and in Santiago city8. These findings suggest that pet dogs could be associated, as sources of infection in cases of diarrhea. This fact has already been described in developed countries1,12,14,16. However, in developing countries there are no documented data linking pet dogs with known cases of Campylobacter enteritis.

Stray dogs are animals that are not in frequent contact with human beings thus suggesting that their participation as sources of infection is limited and that they have greater importance as spreaders of Campylobacter spp. to the environment. At the same time, a contaminated envivonment could provide many opportunities for the transmission of Campylobacter spp. to birds, mammals and humans2. In Valdivia, the 4 biotypes of C. jejuni and the 2 of C. coli were isolated from surface water7.

The high prevalence of dogs which are intestinal carriers, together with the wide distribution of C. jejuni and C. coli biotypes among stray dogs, as well as our findings in surface water7 suggest that envivonmental conditions play an important role in this epidemiological picture. Similar findings have been observed in developing countries among children living in poor, crowded and contaminated urban slums11.

This is probably, an epidemiological aspect that could also be found in relation to other animal populations. Therefore further studies must be undertaken with a view to clarifying the role of environmental sanitary conditions in the spreading of Campylobacter species and the detection of all the links involved in their transmission.